A high-intensity ultra-short pulse laser light source which generates pulsed light having a pulse duration of approximately picoseconds to femtoseconds has a large size, and is normally set on an optical table and used. Respective optical components of the laser light source are held in a free space by a mount with adjusting functions. From this fact, the laser light source has many points to be adjusted, and such adjustments are not easy.
On the other hand, a fiber laser light source using an optical fiber as an optical amplifying medium is increased in energy, and utilization by industry such as laser machining has been attempted. The fiber laser light source mostly solves the above-described problem, and in the case of continuous output, a fiber laser light source with a high output is realized like a fiber disk laser light source.
However, in the fiber laser light source, the optical fiber limits the beam cross section to be small, so that in a pulsed output, the pulse energy is limited to approximately several μJ, and a high output cannot be realized. Thus, there is no laser light source which is small in size, has a high output, is excellent in stability, and is easily adjusted; therefore, in actuality, use of the high-intensity ultra-short pulse laser light source is limited to research purposes.
As an optical amplifying device which is intended to be downsized and stabilized, configurations disclosed in Patent Document 1 and 2 are known. The optical amplifying device disclosed in Patent Document 1 is capable of conveniently increasing the resonator length, and has a small-sized optical resonator. The optical amplifying device disclosed in Patent Document 2 includes an optical resonator having a polarization maintaining optical fiber provided on a resonant optical path separately from an optical amplifying medium.    Patent Document 1: Japanese Patent No. 3540741    Patent Document 2: Japanese Published Unexamined Patent Application No. 2004-165652